But with the update, Apple's also moving to push some of the apps you use -- and love -- to the wayside like so much rubbish. Here's what's at the top of the OS X Mountain Lion hit list.

Adium & AIM

Most folks probably ditched the plain old AIM client for iChat or Adium ages ago, but Messages obliterates any reason for hanging onto it. Adium's also under the gun, since its main selling points were its Growl compatibility and easy-to-navigate cross-platform logs. The new Messages has Notification Center banners and an embedded hub to nullify Adium's Growl integration. And if you're a log-fiend, then syncing from mobile devices to your desktop is a really nice addition.

Then there's the fact that if you want to loop in FaceTime and iMessages to your chat life, you've got no choice but Messages. That's huge because of just how good iMessage is; it's the richest and best IM protocol, and you'd be crazy to ditch it if you've got an iPhone or iPad. Messages also has the added benefit of being actively maintained by Apple; Adium's mostly left to rot. At this point, the only thing left for Adium, it seems, is skin and icon modding. Which is something, I guess?

Dropbox

It's well-known that Steve Jobs lusted after Dropbox, reportedly trying to buy it for $US800 million and aggressively integrate it into iCloud. "[Dropbox is] a feature, not a product", and all. But Dropbox stood pat, and now Apple's moving on without it, nudging it into obsolescence.

iCloud, to this point a niche feature, is finally getting its crap together. Documents syncing across all your account-enabled machines is a big deal, and covers a lot of the functionality of Dropbox. Cross-platform functionality will keep iCloud from taking over entirely, and Dropbox has always had seamless integration in OS X. That, combined with the fact that iCloud still doesn't do massive files, means that Dropbox ain't going anywhere anytime soon. But its turf has definitely been moved in on in a dramatic way.

SMS

Yes, you've still got a few friends or family members clinging to their dumbphones. But with Messages, communication with them is going to be off on its own island. That's because even though Messages rolls up virtually every communication platform into one hub, it logs SMS interactions separately. Every communication but SMS lands in one place, and cross-platform services like Gtalk are becoming more and more common on phones. Among iOS users, there's really no reason to use SMS any more. And that's a big chunk of bill-paying phone customers.

Growl

Notification Center is like a more legible Growl. It takes Growl's core functionality -- pop-up notifications in the upper right corner of your screen -- and improves on it. Growl's Rollup has total integration with all of Apple's native apps, but it keeps all notifications that happen while you were away in the centre of your screen, where they sit until you dismiss them. Notification Center's hidden sidebar seems like a much more elegant and non-intrusive way to get the same information. And it will be nice to be able to glance at notifications that you didn't get a chance to glance at while you were concentrating on something else.

The result is a better experience for you, especially with the API being made available for all third-party apps, but there's some small irony that the latest big cat's killing off Growl.

Anything Not in the App Store?

We're nowhere near this being a reality, but one of the curious parts about the Gatekeeper feature is what it might mean for the future of OS X app downloads. Gatekeeper allows you to set varying levels of "security" for your app downloads. Its intention is to limit the amount of malware that a less savvy user can expose himself to, by simply not allowing an untrusted download to be installed.

Apple claims it's not trying to "curate" the web, and being able to limit what your luddite relatives can download certainly has a lot of value. But speculation that it might be planting the seeds for a future where Apple controls all software that's installed on a machine -- as it does on iOS devices -- isn't totally unwarranted. Just something to chew on.

But! Twitter Looks Awesome

On the other hand, Twitter integration looks wonderful. Sharing things directly from native applications is great, and the promise that similar functionality might come to Facebook, Flickr and other networks makes it clear that the future of OS X isn't all destruction, terror and mayhem.

The lesson, I guess, is to get big enough that Apple's cats can't devour you whole.